Ingot withdrawal means for continuous casting



R. H. PARFIT A ril 15, 1969 INGOT WITHDRAWAL MEANS FOR CONTINUOUSCASTING Sheet 1 of 2 Filed Feb. 15, 1967 INVENTOR RAYmem: H PAlzFvrApril 15, 1969 R. H. PARFIT 3,438,426

INGOT WITHDRAWAL MEANS FOR CONTINUOUS dASTING Filed Feb. 15, 1967 Sheet2 of 2 iNVENTOR RRYMuNb H. Pmrl'f BY 7 w a c fl wzzw ATTORNEYS UnitedStates Patent Ofice 3,438,426 Patented Apr. 15, 1969 U.S. Cl. 164-282 4Claims ABSTRACT OF THE DISCLOSURE An ingot withdrawal mechanism for acontinuous casting plant, in which the ingot is withdrawn from the chillmould horizontally or near-horizontally in a series of intermittentsteps with intermediate dwell periods by means of a motor-driven Genevamechanism whose output shaft drives a pair of pinch rollers gripping theingot. The Geneva mechanism is provided with a positive interlock tohold the slotted driven wheel stationary when the eccentric driving pinis disengaged from the slots of the driven wheel.

Background of the invention This invention relates to the field of thecontinuous casting of metals, using apparatus in which the liquid metalis fed from a furnace, ladle or other container into an open-ended chillmould whose casting axis is horizontal or near horizontal at thedischarge end from which the solidified or partly-solidified metal iswithdrawn intermittently as a continuous ingot.

It has been proposed to impart the intermittent withdrawal motion to theingot by starting and stopping a motor driving the ingot withdrawalmeans; or alternatively as in British patent specification No. 812,356by connecting the withdrawal means to the ingot during a portion only ofa reciprocating cycle.

The former method has the disadvantage that the acceleration is noteasily controlled and may snatch the ingot at the start of thewithdrawal, causing rupture of the ingot skin in the mould if used atother than very slow speeds.

The latter method can produce a smooth low acceleration movement, butrelies on engagement and disengagement of the gripping mechanism underhigh temperature conditions.

It is an object of the present invention to provide an improved cycle ofintermittent withdrawal from the mould.

Summary of the invention According to the present invention, in anapparatus for the continuous casting of metals providing intermittentwithdrawal of the newly-cast ingot from a horizontal or near horizontalmould (inclined at less than 45 to the horizontal), the ingot is grippedby one or more pairs of withdrawal rollers which are connected to therotary driven component of a Geneva mechanism, the rotary driving memberof which is driven by a motor. The Geneva mechanism is a well knownmechanism for deriving an intermittent rotational output movement from acontinuously rotating input member.

The use of the Geneva mechanism in this way has a number of advantages.The intermittent movement imparted by it to the ingot is sinusoidal incharacter, giving the smoothness of motion which has been founddesirable in continuous casting. The movement of the ingot is positiveand precise; there can be neither over-run nor run-back. The ratio ofmovement time to stationary time can be varied by varying the number ofstationing slots on the driven wheel of the Geneva mechanism withoutaltering the form of the movement. This is not, of course, possible witha reciprocating mechanism. The mechanism, apart from the rollersthemselves which are in constant contact with the hot ingot, can beconveniently sited away from undue heat.

Brief description of the drawing The invention may be carried intopractice in various ways, but one specific embodiment will now bedescribed by way of example with reference to the accompanying drawings,in which:

FIGURE 1 is a side view of a horizontal-withdrawal continuous castingplant,

FIGURE 2 is a plan view of the withdrawal unit for the ingot, and

FIGURE 3 is an elevation of the withdrawal unit of FIGURE 2 seen in thedirection of the arrow III in that figure.

Description of the preferred embodiment In the illustrated embodiment acontinuous casting installation comprises a tundish 10 mounted on aframe 11 within a main vacuum enclosure 12, the pouring nozzle 13 of thetundish 10 leading into one open end of a horizontal mould 14 which issecured to the side of the tundish 10. The other open end of the mould14 leads into a secondary vacuum chamber 15. A melting furnace 16 ispivotally mounted within the main vacuum enclosure 12 and can be tilteddown to pour liquid metal 17 into the tundish 10 through the open top ofthe latter. The metal discharged through the pouring nozzle 13 of thetundish 10 into the mould 14 is chilled in the mould and emerges as acontinuous horizontal ingot 16 which extends through the secondaryvacuum chamber 15 and emerges via a vacuum gland 18 to be received onsupporting rollers 19 outside the main vacuum chamber 12. The horizontalingot 16 is gripped beyond the supporting rollers 19 by a pair ofopposed pinch rollers 25 of a withdrawal unit 21 by which the newly castcontinuous ingot is Withdrawn longitudinally in the horizontal directionfrom the mould 14.

The withdrawal unit 21 is shown in detail in FIGURES 2 and 3 andcomprises a frame 22 supporting a pair of journal bearing 23 in whichare journalled the shafts 24 of a pair of pinch rollers 25 constitutingthe withdrawal rollers by which the ingot 16 is gripped to withdraw itfrom the mould. The withdrawal rollers 25 are mounted one verticallyabove the other as shown in the drawings, so as to engage the top andbottom surface of the ingot 16.

The two withdrawal rollers 25 are coupled through individual worm geardrives 26 to a vertical intermediate shaft 27 journalled in bearingsmounted on a cross member 28 of the frame 22, the worms being mountedcoaxially on the intermediate shaft 27 for rotation thereby. Theintermediate shaft 27 is driven through a chain or belt drive 29 by theoutput shaft 30 of a Geneva mechanism 31 which is journalled in bearingscarried by a bracket 32 on the side of the frame 22, the slotted drivenmember 33 of the Geneva mechanism being mounted on .the output shaft 30to drive the latter. The driven member 33 of the Geneva mechanism inthis case has six radial slots 34 at equal angular spacings, these slotsbeing entered successively by the eccentric driving pin 35 of thedriving wheel 36 of the Geneva mechanism, which driving wheel 36 isitself mounted on a driving shaft 37 also journalled in bearings in thebracket 32. The driving pin 35 is fitted with a hardened steel brush toreduce Wear between it and the driven wheel 33. The driving shaft 37 isdriven through a belt or chain drive 38 and a variable speed gear box 39by an electric motor 40 mounted on the bottom of the frame.

Thus the two pairs of withdrawal rollers will be in termittently drivenby the motor 40 acting through the variable gear box 41 and the Genevamechanism 31 during the successive periods when the driving pin 35 is inengagement with a slot 34, alternating with dwell periods when the pin35 has left one slot 34 and has not yet returned to enter the followingslot 34. These alternate driving periods and dwell periods will produceintermittent successive withdrawal steps of the ingot 16 from the mould,the relative duration of the withdrawal steps and the intervening dwellperiods being determined by the geometry of the Geneva mechanism 31. Theoverall fre quency of the cycles of withdrawal and dwell of the ingotmay be varied by means of the gear box 39, without alteration of theamplitude of the steps.

The driving wheel 36 also'carries a coaxial disc sector 41 mounted forrotation with it, and the slotted driven member 33 is formed in itsperiphery with a number of concave recesses 42 respectively located atpoints of its periphery between the radial slots 34. During the portionof each revolution of the driving wheel 36 during which the driving pin35 is out of engagement with any radial slots 34 of the driven member33, the arcuate periphery of the rotating disc sector 41 is slidinglyengaged in one of the concave peripheral recesses 42 of the slotteddriven member 33 so as to hold the latter stationary and positively toprevent its angular rotation for the duration of the dwell periodbetween successive angular stepping movements. As the eccentric pin 35of the driving wheel 36 comes into engagement with the next radial slot34 however, the disc sector 41 will turn out of engagement with theconcave recess 42 of the slotted driven member 33 to free the latter forrotation by the eccentric pin through the next step.

The characteristic of the stepping cycle and the amplitude of the linearsteps of the ingot 16 can be altered by replacing the relevantcomponents of the Geneva mechanism by others having difi'erentcharacteristics.

For example a driving wheel 36 having its eccentric driving pin 35 at adifferent radius, and/or having two or more circumferentially-spacedeccentric driving pins 35, may be used, and the driven wheel 35 may bereplaced by one having other than six slots 34, which may be ofnonradial disposition, for example curved longitudinally.

If desired a second pair of withdrawal rollers may be provided to gripthe ingot 16 beyond the first pair of rollers, this second pair ofrollers being driven by a separate chain or belt drive 29 from the sameGeneva mechanism .31.

What I claim as my invention and desire to secure by Letters Patent is:

1. Apparatus for the continuous casting of metals, comprising anopen-ended chill mould and means for intermittently withdrawing anewly-cast ingot from the mould in a continuous length and in adirection inclined at less than 45 to the horizontal, which withdrawalmeans comprises a motor-driven Geneva mechanism driving at least onepair of withdrawal rollers between which the ingot is gripped, therotary driving member of the Geneva mechanism being coupled to a drivingmotor for continuous rotation thereby and the withdrawal rollers beingcoupled to the slotted rotary driven component of the Geneva mechanismso as to be driven intermittently thereby.

2. Apparatus for the continuous casting of metals, comprising a chillmould having an open inlet end and an open withdrawal end, means forpouring molten metal into the open inlet end of the mould, andwithdrawal means for intermittently withdrawing a newlycast ingot in acontinuous length from the withdrawal end of the mould at an angle ofinclination of less than 45 to the horizontal, which withdrawal meanscomprises at least one pair of Withdrawal rollers adapted to grip theingot between them, and a motor-driven Geneva mechanism coupled to therollers to drive them intermittently, the Geneva mechanism having arotary driving member coupled to a driving motor for continuous rotation thereby, a a rotary driven member journalled for rotation about anaxis spaced from and parallel to that of the driving member and coupledto the withdrawal rollers by transmission means to drive the two rollersof each pair in opposite angular directions, a series ofangularlyspaced, generally radially-extending stationing slots beingformed in the rotary driven member and each stationary slot being openat one end at the circumference of the driven member, and at least onedriving pin being mounted eccentrically on the rotary driving member forengagement in successive slots of the rotary driven member to turn thelatter intermittently through successive angular steps alternating withstationary dwell periods.

3. Apparatus as claimed in claim 2 including means for automaticallylocking the driven rotary member of the Geneva mechanism againstrotation during the said dwell periods, which locking means comprises aquadrant rigidly attached coaxially to the rotary driving member forrotation therewith, the rotary driven member being formed between themouths of the stationing slots with a series of concave recesses in itsperipheral marginal portion, and the quadrant being slidingly engaged inone of the said recesses to lock the driven member against rotationduring each dwell period.

4. Apparatus as claimed in claim 2 including variablespeed geartransmission means operatively connected between the driving motor andthe rotary driving member of the Geneva mechanism.

References Cited UNITED STATES PATENTS 1,442,021 1/ 1923 Workman 74-4362,584,704 2/1952 Horn 164-282 X 2,815,551 12/1957 Hessenberg et al.16483 3,158,522 11/ 19 64 Dreher 226152 X 3,290,734 12/ 1966 Wertli164-282 J. SPENCER OVERHOLSER, Primary Examiner. R. S. ANNEAR, AssistantExaminer.

U.S. Cl. X.R. 226152

